Depressor bar type recording apparatus

ABSTRACT

A depressor bar type chart recording apparatus of the type having a dotting apparatus axially slidable on a rotating drive shaft and being activated by the rotating drive shaft to sequentially impress different colored ink dots upon the chart at selected axial locations. The dotting apparatus has a slide tube rotating with the drive shaft and carrying a dotting cam and a sequencing cam. The frame for the dotting apparatus includes a sliding portion coupled to the slide tube for axial motion therewith, and a swinging portion pivoted to the sliding portion and having a cam follower engaging the dotting cam for causing the swinging portion to be pivoted. A dotting shaft is carried by the swinging portion of the frame, and has at one end a dotting wheel with circumferentially spaced dotting needles brought into contact with the chart as the frame swings, and at the other end sequencing means engaging the sequencing cam and intermittently rotating the dotting needles into position for contacting the chart. A plate is pivotally mounted on the swinging frame portion, and carries an inkpad shell which is rotated along with the dotting shaft and is brought into contact with the dotting wheels as the plate moves inertially upon movement of the swinging frame portion.

aselie et al.

[ 1 DEPRESSOR BAR TYPE RECORDHNG APPARATUS [75] Inventors: Takefumillasebe; Arata Talrizawa,

thqtTplsvoJamn [73] Assignee: Yokogawa Electric Works, Tokyo,

Japan [22] Filed: July 24, 1972 [21] Appl. No.: 274,446

[30] Foreign Application Priority Date July 29, 1971 Japan 46/67538 July29, 1971 Japan 46/6753? July 29, 1971 Japan..'.... 46/67536 [52] lJ.S.Cl 346/46, 346/17, 346/141 [51] int. Cl. Gllld 15/16 [58] Field ofSearch 346/46, 61, 141,

[56] References Cited UNITED STATES PATENTS 2,191,673 2/1940 Moore346/46 3,611,412 10/1971 Gibby 346/141 X 3,693,180 9/1972 Hasebe et a1.346/141 X i, t i, I

[4s] @ept. as, 1973 Primary Examiner-Joseph W. l-lartary Attorney-RolandT. Bryan et a1.

[ 5 7 ABSTRACT A depressor bar type chart recording apparatus of thetype having a dotting apparatus axially slidable on a rotating driveshaft and being activated by the rotating drive shaft to sequentiallyimpress different colored ink dots upon the chart at selected axiallocations. The dotting apparatus has a slide tube rotating with thedrive shaft and carrying a dotting cam and a sequencing cam.

The frame for the dotting apparatus includes a sliding portion coupledto the slide tube for axial motion therewith, and a swinging portionpivoted to the sliding portion and having a cam follower engaging thedotting cam for causing the swinging portion to be pivoted. A

dotting shaft is carried by the swinging portion of the frame, and hasat one end a dotting wheel with circumferentially spaced dotting needlesbrought into contact with the chart as the frame swings, and at theother end sequencing means engaging the sequencing cam andintermittently rotating the dotting needles into position for contactingthe chart. A plate is pivotally mounted on the swinging frame portion,and carries an inkpad shell which is rotated along with the dottingshaft and is brought into contact with the dotting wheels as the platemoves inertially upon movement of the swinging frame portion.

7 Q ma fiEmail-sidelines. a

Patented Se t; 25, 1973 3,761,949

3 Sheets-Sheet 1 Patented se 't. 25, 1973 3,761, 19

3 Sheets-Sheet 2 DEPRESSOR BAR TYPE RECORDING APPARATUS BACKGROUND OFTHE INVENTION 1. Field of the Invention The present invention relates todepressor bar type chart recording devices. Such devices are useful, forexample, in control processes aimed toward achieving a uniformtemperature inside a large furnace, where it is often the practice thatone recording meter is used for recording on a single chart thetime-varying temperature measured by a plurality of temperaturedetectors suitably located inside the furnace.

One such type of recording meter is the depressor type, generally usedin connection with automatic nullbalancing. The depressor bar typerecording device comprises a dotting wheel with dotting needlescorresponding in number to the number of measuring points. The dottingwheel is intermittently rotated to bring the inked dotting needlessuccessively into contact with the recording chart to record themeasured values. The present invention relates to this type of recordingapparatus.

2. Description of the Prior Art One generally known depressor bar typechart recording mechanism has a swinging frame moved by a lever which issupported at one end by the swinging frame and pivoted by a cam. Thedotting wheel is made of a metal, with a plurality of dotting needlesimplanted at regular intervals around the wheel body. Under each needlepositioned for dotting is a fork-shaped guide member for holding theneedle in position before it dots the chart. Needles are inked with aninkpad shell mounted by the use of screws.

This conventional mechanism is complicated in construction and heavy.Furthermore, because the inkpad shell is fastened to the frame withscrews, a screwdriver must be available for its mounting or dismounting.Positioning of the inkpad is supposed to be accurate relative to theclotting needles; however, this is difficult in the prior art, becauseof awkward construction. Still further, the guide member for the dottingneedle necessitates an intricate structure for the dotting mechanism asa whole. As a result, recording instruments incorporating this mechanismare structurally complicated, they are inconvenient to use, theirproduction cost is high, the size of the instrument is large, andportability decreases.

SUMMARY OF THE INVENTION A principal object of the present invention isto provide a depressor bar type chart recording device which isstructurally simple, small in size, light in weight, and easy tooperate, free of the drawbacks in the prior art.

Briefly, the depressor bar chart recording device of this invention ischaracterized by a frame with a sliding portion and a swinging portion,both of which, for example, are die-cast ofa light metal. The swingingframe portion is pivotally carried by the sliding frame portion, engagesat one end with a cam, and is allowed to swing directly in response tothe cam rotation. In other aspects, dotting wheel and a plurality ofdotting needles are molded into one unit with a hard synthetic resinimplanted with a metal insert. The front of the dotting wheel hassymbols, such as digital numbers, indicating the individual measuringpoints. A lens window, through which any digital number on the dottingwheel can be clearly observed, is provided. A compact, builtin detentmechanism having a ball and a spring is disposed where the dotting wheelis in contact with the swinging frame portion, and serves to stop thedotting wheel in position during its intermittent rotation, thus truingeach clotting needle before it touches the chart. The inkpad shell ismounted on a shaft coupled for rotation with the dotting wheel having apin implanted in the diametral direction. The legs of the pin exposed onboth sides of the shaft are different in length, and a compressionspring is fitted round the shaft. This arrangement allows the inkpadshell to be accurately set in position relative to the mounting shaftand dotting needles, without using a special tool.

Other objects, aspects and advantages of the present invention will bepointed out in, or apparent from, the detailed description hereinbelow,considered together with the following drawings.

DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of recordingapparatus according to the invention;

FIG. 2 is a side view of the apparatus of FIG. 1 with the dottingelements in their raised position;

FIG. 3 is a plan view;

FIG. 4 is a perspective view illustrating the frame used for theapparatus of FIG. ll,

FIGS. 5(A) (I) through 5(C) (2) are partial plan and elevationaldiagrams showing steps in the sequencing cam movement; and

FIG. 6 is a sectional side view showing the apparatus of FIG. l with thedotting elements in their depressed position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 through 3,the dotting apparatus according to the invention is arranged formovement along a supporting rod 1 and a driving shaft 2 disposed inparallel with the rod 1. The rod l and shaft 2 are supported at bothends by a conventional instrument housing frame (not shown), and thedriving shaft 2 has a keyway 2a formed in the axial direction.

The frame F for the clotting apparatus, illustrated separately in FIG.4, comprises a slide frame 3 and a swing frame A which are substantiallysquare in shape and die-cast of a light metal such as an aluminum alloy.The swing frame 4 has a rear panel 41 from which supporting members 32and 43 extend on both sides. The supporting member 43 has a bearingroller 44 which is positioned in contact with a dotting cam 57 to causeswing frame Al to swing, as will be specifically described below. Thesupporting members 42 and 43 fit into the slide frame 3, and screw-pins33 and 34, which are fastened on side panels 311 and 32 of the slideframe 3, hold the supporting members 32 and 4l3 and enable the slideframe 3 and swing frame a to swing with respect to one another.

As shown in FIGS. 2 and 3, a roller 35, mounted on a front panel 36 ofthe slide frame 3, is in forward contact with the supporting rod K, andprovides support for the slide frame 3. A slide tube 5, fitting overdrive shaft 2, is rotatably attached to the slide frame 3 by means ofplates 31 and 52 attached to slide frame 3 with screws. Both ends ofslide tube 5 are fitted with rings 33 and 33 which hold roller bearings35 and 36 in keyway 2a drive shaft 2, and thus the slide tube 5 iscoupled to the driving shaft 2 in such a manner that the slide tubereceives the rotating force from the driving shaft 2 and can slide withthe slide frame 3 in the axial direction.

A depressor cam 57 having a recessed part 57a, and a changeover cam 58having a notch 58a and a feed roller 58b are attached to the slide tube5. The swing frame 4 has its center of gravity forward of the screwpins33 and 34, and thus the roller 44 on swing frame 4 keeps contact withthe lower circumference of the depressor cam 57 by gravitational forces.

The sliding motion of the dotting apparatus is limited by cylindricalstops 38 and 39 on the sides of slide frame 3 (FIGS. 1 and 3), each ofwhich carries a rubber cylinder arranged to hit the instrument housingframe on either side as the dotting frame F swings from side to side,and thus serves as a buffer in stopping the dotting frame.

A dotting shaft 6, rotatably supported by the swing frame 4, isperpendicular to the driving shaft 2 and equipped at one end with anindexing or sequencing plate 7 having twelve circumferentially spaced,axially extending pins 71. The sequencing plate 7 is disposed at a rightangle to sequencing cam 58 and engages the sequencing cam in aperipheral position where two of the 12 pins 71 always lie outside theplane of the cam 58 (i.e., below the cam as shown in FIG. 3). At itsother end, dotting shaft 6 mounts a dotting wheel 8 having a trapeziodalsection and having twelve individual dotting needles 81 disposedradially therearound. As shown in FIG. 6, the clotting wheel 8 is moldedof hard synthetic resin with a central metal insert 82 to receivedotting shaft 6. The dotting wheel 8 is accurately aligned by means of adetent mechanism 60 having a ball and a biasing leafspring disposedwhere the dotting wheel 8 is in proximity to the swing frame 4 (FIG. 6).The detent mechanism 60 serves to true each of the clotting needles 81in position when dotting. As will be described in greater detail below,the front of the dotting wheel 8 is supplied with digital numberscorrelating the individual dotting needles 81 to the measuring circuitswhich supply data the needles are to record.

The dotting needles are inked prior to being impressed on a chart byswinging plate 93 supported by the swing frame 4 with pins 91 and 92, amounting shaft 94 rotatably coupled to the plate 93, a bevel gear 95 onshaft 94 which meshes on a line connecting pins 91 and 92 with a bevelgear 61 secured to dotting shaft 6, and an inkpad shell 10 which isdismountably fitted on the shaft 94. As shown in FIGS. 3 and 6, theswinging plate 93 has a sloped portion 93a which rests against the endof an L-shaped plate 37 provided on swing frame 4. Twelve cells 11, eachhaving an opening facing toward the swing frame 4, are formed radiallyin the inkpad shell 10 and accommodate inkpads 12, soaked respectivelywith ink of different colors to be supplied to dotting needles 81. Theinkpad shell 10 is removably attached to mounting shaft 94 upon a collar940, on which a flat compression spring 13 of corrugated disk shape isfitted. A pin 14 is implanted in the mounting shaft 94 in the diametraldirection, and as shown in FIG. 3, the exposed portions 14a and 14b ofthe pin 14 are different in length on opposite sides of the shaft 94.The inkpad shell 10 receives shaft 94 and pin 14 in a mounting hole 15which comprises a collar receiving hole 15 into which the collar 94:: ofthe mounting shaft 94 is fitted, a pin receiving hole 15b having ada-shaped outline duplicating the outer irregular configuration ofmounting shaft 94 and pin 14, and an internal pin securing hole 15dshaped like an 8" and having its bottom surface partly sloped to form aramp.

Secured to slide frame 3 is a bracket 20 having a square hole 20abeneath dotting wheel 8, and a pointer 21 fastened in front of dottingwheel 8 and in front of a stationary scale 22 indicating axial position.The pointer 21 is made of a transparent acryl resin and has a verticalsight line 211 colored, for example, in red. A rough surface area 212irregularly reflects light, and surrounds a square window 213 oppositethe number in the lowest position on the dotting wheel 8, correspondingto the dotting needle in position for marking. As shown in FIG. 1,window 213 has a convexed portion forming a lens to enlarge the image ofthe number being viewed.

The dotting apparatus is positioned above a chart 24 transported on achart guide plate 23. Axial position of the dotting apparatus isdetermined by positioning elements including a steel band 25 and astranded metal wire 26, connected at one end to the slide frame 3, andat the other end to a pulley coupled to the rotating shaft of abalancing motor associated with a conventional automatic null-balancingmechanism (not shown in Drawings). Lugs 45 and 46 in the rear of theslide frame 3 are equipped with a suitably shaped actuating plate or thelike which moves with the clotting frame F and turns on or off amicroswitch to allow an alarm mechanism to operate if the measuredvalues exceed predetermined limits.

The chart recording apparatus having the dotting apparatus describedabove is operated in the following manner.

Indexing of the Dotting Needles and Dotting of Chart The operation ofthe apparatus will be described beginning with a starting position inwhich the roller 44 is in contact with the circumference of the dottingcam 57, and the sequencing cam 58 is positioned relative to thesequencing plate 7 as shown in FIGS. 5(A) (1) and (2), with one 81-] ofthe dotting needles 81 being located in the lowermost position of thedotting wheel 8, opposite recording chart 24. When the driving shaft 2rotates in the direction of arrow a, the sequencing cam 58 is rotatedaccordingly, the feed roller 58b is brought into contact with pin 71-1of the sequencing plate 7 and feeds the pin 71-1 upwardly, therebyrotating the sequencing plate 7 in the direction of arrow b, as shown inFIGS. 5(B)(1) and (2). As pin 71-1 is thus fed, the following pin 71-2moves outwardly across the plane of sequencing cam 58 through the notch58a therein. At the same time, the preceeding pin 71-0 moves inwardlyover the plane of sequencing cam 58. Although sequencing cam 58continues to rotate, the sequencing plate 7 stops rotation as shown inFIG. 5(C) (1) and (2).

This intermittent rotation of the sequencing plate 7 causes the dottingwheel 8 to rotate by one-twelfth of a revolution and to feed the nextdotting needle 81-2 to the lowermost position of the dotting wheel 8,whereupon the dotting needle 81-2 faces the chart 24. The stop positionof the dotting wheel 8 is determined by detent mechanism 60, whichserves to true the dotting needle 81-2 relative to the chart 24.

The measuring circuit related to the dotting needle 81-2 is thenautomatically null-balanced, and the dotting frame F is positionedaxially on the driving shaft 2, with the measured value being indicatedon the scale 22 by the pointer 21. At this moment the roller 44 entersthe recessed portion 57a of the dotting cam 57, thereby swinging theswing frame 4 on the screw pins 33 and 34 in the direction of arrow d.As a result, the dotting needle 81-2 touches the recording chart 24, toinstantaneously record the measured value. FIG. 6 shows the recordingapparatus as it appears at this stage in the dotting operation.

When the driving shaft 2 further rotates and again assumes thecircumferential position of FIGS. 5(A) (ll) and (2), the feed roller 58bfeeds the next pin 71-3 upward, to rotate the clotting wheel 9 byanother onetwelfth revolution. As a result, the next dotting needle 81-3faces the recording chart 24. The corresponding measuring circuit isnull-balanced, and the next dot is marked on the chart as describedpreviously. These operations are repeated twelve times (or the number oftimes necessary to utilize each dotting needle) to form one cycle of therecording operation which the recording apparatus of this inventionperforms.

The digital number on the dotting wheel 8 indicating each measuringpoint can be easily observed through the lens window 2113 of the pointer21, except while the rotary wheel is in motion. Inkpad Indexing andDotting Needle Inking When the dotting shaft 6 rotates intermittently toindex the dotting wheel 8 as described above, the rotating force isconveyed to the mounting shaft 94 through the bevel gears 61 and 95, andthe inkpad shell secured to the mounting shaft 94 is also intermittentlyrotated. The inkpads 112 are thus indexed synchronously with theindexing of the clotting needles.

As described above, the movable plate 93 is capable of swinging aboutthe axis of pins 911, 92, and upon movement of the swing frame 4 in thedirection of arrow d, the movable plate 93 swings in the direction ofarrow d because the sloped portion 93a is in contact with the stationaryplate 37, and the sloped portion 930 is thus prevented from lowering.Accordingly, the inkpad 12-8 in the frontmost position of the inkpadshell is pressed against the dotting needle fill-h located at the top ofthe dotting wheel (which occurs when the dotting needle 811-2 is in thelowermost position). When dotting shaft 6 rotates by one-twelfthrevolution to feed dotting needle 81-9 to the frontmost position of thedotting frame F, the inkpad shell l0 also rotates by onetwelfthrevolution, and the next inkpad 1129 faces the dotting needle 91-9. Thisdotting needle is inked as the inkpad shell next swings during motion ofthe swing frame 4. In this fashion the same dotting needle is alwaysinked in the same color, and error in inking is eliminated.Mounting/Dismounting of the inkpad Shell The inkpad shell is mounted inthe following manner. The inkpad shell lltl is first placed on themounting shaft 94, centering the mounting hole 115 about the mountingshaft 94 and inserting pin 14 through the d: shaped pin receiving hole15b with the different length pin portions 14a and 14b matching thedifferent length pin openings in hole 15b. When the pin 14 reaches the8-shaped turning hole 15d, the inkpad shell is rotated by an angle ofabout 90 in the direction opposite to arrow 0, causing the pin 114 toride up on ramp surface 15:: and causing inkpad shell lltl to oppose theexpansion force of the spring 13. The spring lid is graduallycompressed, and the inkpad shell W is fully secured to the mountingshaft 94 at the point when the pin portions 114a and 14b come intocontact with the side walls of the 8-shaped revolving hole 15d.

Because the legs Ma and 14b of the pin 14 have different lengths, andbecause the pin receiving hole 15b conforms to the shape of the pin,possibilities for misaligning the inkpad shell 10 on the mounting shaft94 are completely, eliminated. Since the side wall of the 8- shaped holellSd has a constant position relative to the inkpads 112, the inkpadsautomatically are positioned in proper correspondence to the individualdotting needles M simply by mounting the inkpad shell 119 on the shaft94. When the mounting shaft 94 rotates, the rotational force causes pinportions 114a and 14b to push against the side walls of hole 11511, andthis insures the inkpad shell M will not become loose due to indexingmovement of the inkpad shell. The inkpad shell 10 can be dismounted byrotating the inkpad shell W in the direction of arrowc, to return thepin portions 114a and 14b into alignement with the pin openings in pinreceiving hole I517.

The recording apparatus of this invention has a number of advantageousfeatures, summarized below.

1. The dotting apparatus consists essentially of only a slide framehaving a slide tube, a dotting wheel equipped with dotting needles, anda swing frome associating a dotting shaft, a sequencing plate and aninkpad mechanism. Hence the number of necessary components is minimized,overall construction is simplified, size is reduced, and production costis lowered.

2. The dotting frame itself consists essentially of only a slide frameand a swing frame which is rotatably coupled to the slide frame andswung directly by a roller means. This construction further enhances theadvantages of simplicity and economy noted above.

3. The dotting wheel carrying the dotting needles, as well as bevelgears of the inkpad mechanism, may be formed into one unit by the use ofsynthetic resin. This serves to simplify construction and to reduceweight.

4. The stop positions of the intermittently rotating dotting wheel areaccurately determined by a detent mechanism of simple construction,using the combination of a ball and a spring. This arrangement dispenseswith the need for another frame or means for determining the position ofeach dotting needle, helps reduce the size of the device, and assures anaccurate dotting action.

5. Attachment of the inkpad shell is effected by means of a pin on themounting shaft exposing two legs of different length, and a compressionspring is fitted round the pin. This pin-and-spring arrangement servesto simplify the inkpad shell mounting mechanism and facilitatesmounting/dismounting the inkpad shell.

6. The foregoing pin arrangement allows the inkpad shell to restsecurely in position whenever it is mounted. Hence the inkpadpositioning is always kept accurate relative to the position of eachdotting needle.

7. A lens window is provided on the pointer, thus permitting easyreadout of the number indicating the corresponding measuring point eventhough the overall size of the depressor mechanism is minimized.

By following the principles of the invention, a very lightweightapparatus may be obtained. For example, the weight of an entire unitmanufactured according to this invention was only grams.

Although specific embodiments of the invention have been disclosedherein in detail, it is to be understood that this is for the purpose ofillustrating the invention,

and should not be construed as necessarily limiting the scope of theinvention, since it is apparent that many changes can be made to thedisclosed structure by those skilled in the art to suit particularapplications.

We claim:

l. A chart recording apparatus of the type having a dotting apparatusaxially slidable on a rotating drive shaft and being actuated by therotating drive shaft to sequentially impress different ink dots upon thechart at selected axial locations wherein the dotting apparatuscomprises:

a slide tube rotating with the drive shaft and slidable therealong;

a dotting cam and a sequencing cam mounted on the slide tube;

frame means including a sliding portion rotatably secured to the slidetube for axial movement therewtih and a swinging portion pivotallysupported by the sliding portion and having cam follower means engagingthe dotting cam for causing the swinging portion to be pivoted thereby;

a dotting shaft carried by the swinging portion of the frame means;

a dotting wheel mounted at one end of the dotting shaft and having aplurality of circumferentially spaced dotting needles thereon;

sequencing means at the other end of the dotting shaft and engaging thesequencing cam for intermittently rotating the clotting shaft and forcausing the clotting needles to be successively brought into positionfor contacting the chart;

a plate pivotally coupled to the swinging portion of the frame means onan axis parallel to the pivoting axis of the swinging frame portion andpivoting inertially as the swinging frame portion is pivoted; and

an inkpad shell removably attached to the pivoting plate and beingbrought into contact with the respective dotting needles as the plate ispivoted inertially with the swinging frame portion;

whereby as the driving shaft is rotated at constant speed, the dottingshaft and wheel are intermittently rotated by the sequencing cam andmeans to bring successive dotting needles to face the chart,

the swinging frame is swung by the clotting cam and follower to impressa dot upon the chart, and the inkpad shell is pivoted to ink anotherdotting needle.

2. A chart recording apparatus as claimed in claim 1 wherein the dottingwheel comprises a central metal insert and wherein the dotting needlesand metal insert are embedded in and joined by molded synthetic resin.

3. A chart recording apparatus as claimed in claim 1 further comprisinga detent mechanism engaging said dotting wheel and having a plurality ofstop positions corresponding to the aligned positions of the dottingneedles facing the chart.

4. A chart recording apparatus as claimed in claim 3, wherein saiddetent mechanism is attached to the swinging frame portion and comprisesa spring-loaded ball.

5. A chart recording apparatus as claimed in claim 1 wherein a scale isdisposed along the path of the dotting apparatus and wherein theclotting apparatus comprises a pointer disposed opposite the scale, thedotting wheel is marked with symbols indicating the individual dottingneedles, and the pointer is arranged with a lensshaped window alignedwith the symbol corresponding to the dotting needle facing the chart.

6. A chart recording apparatus as claimed in claim 1 wherein the inkpadshell is mounted on a shaft coupled for rotation with the dotting shaftto bring corresponding portions of the inkpad in contact with particulardotting needles, and wherein the inkpad shell is removably mounted tothe shaft by means of a pin extending through said shaft with differentexposed lengths on each side of the shaft, the inkpad shell having amounting hole with different length openings on each side of the shaftto receive the pin in only one alignment.

7. A chart recording apparatus as claimed in claim 6 wherein the inkpadshell mounting hole includes an 8- shaped portion with a ramp surface atthe bottom for engaging said pin, the mounting shaft having acompression spring mounted thereon and compressing as the inkpad shellis rotated relative to the mounting shaft and the pin slides along theramp surface.

t i k 1R i

1. A chart recording apparatus of the type having a dotting apparatusaxially slidable on a rotating drive shaft and being actuated by therotating drive shaft to sequentially impress different ink dots upon thechart at selected axial locations wherein the dotting apparatuscomprises: a slide tube rotating with the drive shaft and slidabletherealong; a dotting cam and a sequencing cam mounted on the slidetube; frame means including a sliding portion rotatably secured to theslide tube for axial movement therewtih and a swinging portion pivotallysupported by the sliding portion and having cam follower means engagingthe dotting cam for causing the swinging portion to be pivoted thereby;a dotting shaft carried by the swinging portion of the frame means; adotting wheel mounted at one end of the dotting shaft and having aplurality of circumferentially spaced dotting needles thereon;sequencing means at the other end of the dotting shaft and engaging theseqUencing cam for intermittently rotating the dotting shaft and forcausing the dotting needles to be successively brought into position forcontacting the chart; a plate pivotally coupled to the swinging portionof the frame means on an axis parallel to the pivoting axis of theswinging frame portion and pivoting inertially as the swinging frameportion is pivoted; and an inkpad shell removably attached to thepivoting plate and being brought into contact with the respectivedotting needles as the plate is pivoted inertially with the swingingframe portion; whereby as the driving shaft is rotated at constantspeed, the dotting shaft and wheel are intermittently rotated by thesequencing cam and means to bring successive dotting needles to face thechart, the swinging frame is swung by the dotting cam and follower toimpress a dot upon the chart, and the inkpad shell is pivoted to inkanother dotting needle.
 2. A chart recording apparatus as claimed inclaim 1 wherein the dotting wheel comprises a central metal insert andwherein the dotting needles and metal insert are embedded in and joinedby molded synthetic resin.
 3. A chart recording apparatus as claimed inclaim 1 further comprising a detent mechanism engaging said dottingwheel and having a plurality of stop positions corresponding to thealigned positions of the dotting needles facing the chart.
 4. A chartrecording apparatus as claimed in claim 3, wherein said detent mechanismis attached to the swinging frame portion and comprises a spring-loadedball.
 5. A chart recording apparatus as claimed in claim 1 wherein ascale is disposed along the path of the dotting apparatus and whereinthe dotting apparatus comprises a pointer disposed opposite the scale,the dotting wheel is marked with symbols indicating the individualdotting needles, and the pointer is arranged with a lens-shaped windowaligned with the symbol corresponding to the dotting needle facing thechart.
 6. A chart recording apparatus as claimed in claim 1 wherein theinkpad shell is mounted on a shaft coupled for rotation with the dottingshaft to bring corresponding portions of the inkpad in contact withparticular dotting needles, and wherein the inkpad shell is removablymounted to the shaft by means of a pin extending through said shaft withdifferent exposed lengths on each side of the shaft, the inkpad shellhaving a mounting hole with different length openings on each side ofthe shaft to receive the pin in only one alignment.
 7. A chart recordingapparatus as claimed in claim 6 wherein the inkpad shell mounting holeincludes an 8-shaped portion with a ramp surface at the bottom forengaging said pin, the mounting shaft having a compression springmounted thereon and compressing as the inkpad shell is rotated relativeto the mounting shaft and the pin slides along the ramp surface.